clarify docs for BodyEncoding::encoding() (#2258)

actix-files/src/named.rs

@@ -235,6 +235,8 @@ impl NamedFile {
     }
 
     /// Set content encoding for serving this file
+    ///
+    /// Must be used with [`actix_web::middleware::Compress`] to take effect.
     #[inline]
     pub fn set_content_encoding(mut self, enc: ContentEncoding) -> Self {
         self.encoding = Some(enc);

src/lib.rs

@@ -169,6 +169,8 @@ pub mod dev {
         fn get_encoding(&self) -> Option<ContentEncoding>;
 
         /// Set content encoding
+        ///
+        /// Must be used with [`crate::middleware::Compress`] to take effect.
         fn encoding(&mut self, encoding: ContentEncoding) -> &mut Self;
     }